<!DOCTYPE HTML>
<meta charset=utf-8>
<title>Largest Contentful Paint: Expose cross-origin non-TAO images renderTime.
</title>

<body>
  <script>
    const getLCPStartTime = async () => {
      return await new Promise(resolve => {
        new PerformanceObserver((entryList, observer) => {
          resolve(entryList.getEntries()[0].startTime);
          observer.disconnect();
        }).observe({ type: 'largest-contentful-paint', buffered: true });
      });
    }

    const getFCPStartTime = () => {
      return performance.getEntriesByName('first-contentful-paint')[0].startTime;
    }
  </script>

  <img src='http://b.com/images/blue.png' id='image_id' />
</body>
